Abstract The Plain populations (Amish and Mennonites) originated from founder populations with subsequent genetic bottlenecks and genetic drift; leading to a loss of diversity and an altered genetic disease burden. The Western PA Plain people are among the least genetically characterized Plain communities in the US. This application proposes to use Whole Exome Sequencing (WES) to identify novel genetic disorders in this population. Due to the Plain Populations loss of population genomic complexity, inbreeding, and sociologic isolation, many of the genetic disorders are inherited in autosomal recessive fashion due to homozygous mutations. This genetic makeup as well as the large families will facilitate WES analysis to find candidate variants that can potentially be pathogenic causes of diseases. A multitude of genetic diseases are characterized in the Plain population, and this proposed study will identify additional diseases, enabling a community-centric personalized medicine approach to care based on individual genetic risk. In addition, knowledge of genetic disorders originally developed through study of the Plain Populations, can subsequently be applied in the general population. The central hypothesis is that the Amish and Mennonite communities will allow the identification of novel genetic disorders/pathogenic variants of relevance to the Plain communities, and ultimately the general population. The following aims are proposed: (1) Identification of novel genetic disorders/ disease-causing variants in the Plain communities. The hypothesis is that genetics studies of the Western PA Plain people using WES will allow for continued characterization of novel genetic disorders/pathogenic variants that are relevant to both the Plain and general populations. (2) Performing functional studies for a novel genetic disorder causing dilated cardiomyopathy (DCM). The hypothesis is that the MTCL1 variant (c.82C>G;p.His28Asp) is pathogenic and MTCL1 gene mutations are novel cause of DCM. The candidate is firmly committed to a career in translational genomics research and its implications on the Plain and General populations. She has already worked within the Plain communities, proving her ability to connect with and perform research within these culturally distinct groups. These connections, and her research focus on translational research using WES as a diagnosis tool with functional studies when needed, have already led to the discovery of several mitochondrial disorders and an AK2 gene mutation as a cause of an immunodeficiency with a novel phenotype in the Amish. The primary sponsor is a world recognized expert in the field of Genetics with an outstanding track record of training and with a great working relationship with the candidate. The candidate has developed a comprehensive career development plan to improve her bioinformatics and WES analysis skills, and will learn to perform functional studies related to cardiomyopathy.